Docstoc

System And Method For Recovering Thermal Energy From A Fuel Processing System - Patent 7485381

Document Sample
System And Method For Recovering Thermal Energy From A Fuel Processing System - Patent 7485381 Powered By Docstoc
					


United States Patent: 7485381


































 
( 1 of 1 )



	United States Patent 
	7,485,381



 Dickman
,   et al.

 
February 3, 2009




System and method for recovering thermal energy from a fuel processing
     system



Abstract

Systems and methods for recovering thermal energy from a fuel processing
     system comprising a fuel processor and a fuel cell stack in communication
     with a household that is adapted to apply at least electrical loads, and
     optionally electrical and thermal loads, to the fuel processing system.
     The systems further include a thermal energy recovery system that is
     adapted to recover thermal energy from the fuel processing system and
     which includes a plurality of thermal energy reservoirs. The recovery
     system includes a delivery system that is adapted to selectively deliver
     heat exchange fluid from at least one of the plurality of thermal energy
     reservoirs into thermal communication with the fuel processing system to
     recover thermal energy therefrom. In some embodiments, at least one of
     the thermal energy reservoirs forms at least a portion of a potable hot
     water supply for the household.


 
Inventors: 
 Dickman; Anthony J. (Bend, OR), Edlund; David J. (Bend, OR), Pledger; William A. (Sisters, OR) 
 Assignee:


Idatech, LLC
 (Bend, 
OR)





Appl. No.:
                    
11/084,381
  
Filed:
                      
  March 18, 2005

 Related U.S. Patent Documents   
 

Application NumberFiling DatePatent NumberIssue Date
 10266854Apr., 20056878474
 09476963Oct., 20026465118
 

 



  
Current U.S. Class:
  429/424  ; 429/416
  
Current International Class: 
  H01M 8/04&nbsp(20060101); H01M 8/06&nbsp(20060101)

References Cited  [Referenced By]
U.S. Patent Documents
 
 
 
3765946
October 1973
Werner et al.

3857735
December 1974
Louis et al.

3920416
November 1975
Houseman

3955941
May 1976
Houseman et al.

3980452
September 1976
Krumm et al.

4003343
January 1977
Lee

4098959
July 1978
Fanciullo

4098960
July 1978
Gagnon

4238403
December 1980
Pinto

4302177
November 1981
Fankhanel et al.

4315893
February 1982
McCallister

4381641
May 1983
Madgavkar et al.

4444158
April 1984
Yoon

4472176
September 1984
Rubin

4473622
September 1984
Chludzinski et al.

4533607
August 1985
Sederquist

4567857
February 1986
Houseman et al.

4583583
April 1986
Wittel

4642273
February 1987
Sasaki

4644751
February 1987
Hsu

4650814
March 1987
Keller

4657828
April 1987
Tajima

4659634
April 1987
Struthers

4670359
June 1987
Beshty et al.

4781241
November 1988
Misage et al.

4788004
November 1988
Pinto et al.

4849187
July 1989
Uozu et al.

4865624
September 1989
Okada

4904455
February 1990
Karafian et al.

4946667
August 1990
Beshty

5030661
July 1991
Lywood

5200278
April 1993
Watkins

5229222
July 1993
Tsutsumi et al.

5335628
August 1994
Dunbar

5344721
September 1994
Sonai et al.

5360679
November 1994
Buswell et al.

5366818
November 1994
Wilkinson et al.

5366821
November 1994
Merritt et al.

5401589
March 1995
Palmer et al.

5417051
May 1995
Ankersmit et al.

RE35002
July 1995
Matsubara et al.

5432710
July 1995
Ishimaru et al.

5478662
December 1995
Strasser

5509942
April 1996
Dodge

5527632
June 1996
Gardner

5631820
May 1997
Donnelly et al.

5637414
June 1997
Inoue et al.

5658681
August 1997
Sato et al.

5677073
October 1997
Kawatsu

5741474
April 1998
Isomura et al.

5763113
June 1998
Meltser et al.

5771476
June 1998
Mufford et al.

5780179
July 1998
Okamoto

5795666
August 1998
Johnssen

5798186
August 1998
Fletcher et al.

5811065
September 1998
Sterenberg

5821185
October 1998
White et al.

5858314
January 1999
Hsu et al.

5861137
January 1999
Edlund

RE36148
March 1999
Strasser

5897970
April 1999
Isomura et al.

5932181
August 1999
Kim et al.

5985474
November 1999
Chen et al.

5997594
December 1999
Edlund et al.

6007931
December 1999
Fuller et al.

6022634
February 2000
Ramunni et al.

6042956
March 2000
Lenel

6045933
April 2000
Okamoto

6054229
April 2000
Hsu et al.

6077620
June 2000
Pettit

6103411
August 2000
Matsubayashi et al.

6120923
September 2000
Van Dine et al.

6165633
December 2000
Negishi

6171574
January 2001
Juda et al.

6187066
February 2001
Benz et al.

6190623
February 2001
Sanger et al.

6221117
April 2001
Edlund et al.

6465118
October 2002
Dickman et al.

6878474
April 2005
Dickman et al.



 Foreign Patent Documents
 
 
 
0434562
Jun., 1991
EP

1037423
Jul., 1966
GB

WO 99/65097
Dec., 1999
WO

WO 00/02282
Jan., 2000
WO

WO 00/04600
Jan., 2000
WO



   
 Other References 

English language abstract of Japanese Patent No. 4-163860, 1992. cited by other
.
English language abstract of Japanese Patent No. 5-147902, 1993. cited by other
.
English language abstract of Japanese Patent No. 6176779, 1994. cited by other
.
English language abstract of Japanese Patent No. 7057758, 1995. cited by other
.
English language abstract of Japanese Patent No. 8-287932, 1996. cited by other
.
English language abstract of German language PCT Patent Application Serial No. WO 00/04600, 2000. cited by other
.
Adris, A. M., et al., "A Fluidized Bed Membrane Reactor for the Steam Reforming of Methane," The Canadian Journal of Chemical Engineering, vol. 69, pp. 1061-1070 (Oct. 1991). cited by other
.
Amphlett, J. C., et al., "Simulation of a 250 kW Diesel Fuel Processor/PEM Fuel Cell System," Fifth Grove Fuel Cell Symposium, Commonwealthe Institute, London, U.K., p. 8 (Sep. 22-25, 1997). cited by other
.
Edlund, David J. and William A. Pledger, "The Practical Use of Metal-Membrane Reactors for Industrial Applications," The 1995 Membrane Technology Reviews, pp. 89-97 (Nov. 1994). cited by other.  
  Primary Examiner: Crepeau; Jonathan


  Attorney, Agent or Firm: Dascenzo Intellectual Property Law, P.C.



Parent Case Text



RELATED APPLICATIONS


This application is a continuation of and claims priority to U.S. patent
     application Ser. No. 10/266,854, which was filed on Oct. 7, 2002, issued
     as U.S. Pat. No. 6,878,474 on Apr. 12, 2005, and which is a continuation
     of and claims priority to U.S. patent application Ser. No. 09/476,963,
     which was filed on Jan. 3, 2000, issued on Oct. 15, 2002 as U.S. Pat. No.
     6,465,118, and is entitled "System and Method for Recovering Thermal
     Energy from a Fuel Processing System." The complete disclosures of the
     above-identified applications are hereby incorporated by reference for
     all purposes.

Claims  

What is claimed is:

 1.  A system for recovering thermal energy from a fuel processing system, comprising: a fuel processing system including a fuel processor and a fuel cell stack, wherein the
fuel processor is adapted to receive a feedstock and produce a product hydrogen stream therefrom, wherein the fuel cell stack includes a plurality of fuel cells adapted to receive the product hydrogen stream and to produce an electric current therefrom,
wherein the fuel processing system is in communication with a household that is adapted to apply at least electrical loads to the fuel processing system;  a thermal energy recovery system adapted to recover thermal energy from the fuel processing system
and including a plurality of thermal energy reservoirs that each are adapted to selectively receive and store a supply of heat exchange fluid and a delivery system adapted to selectively deliver heat exchange fluid from at least one of the plurality of
thermal energy reservoirs into thermal communication with the fuel processing system to recover thermal energy therefrom, wherein the plurality of thermal energy reservoirs includes at least one of a swimming pool, a sauna, and a hot tub, and further
wherein at least one of the thermal energy reservoirs forms at least a portion of a potable hot water supply for the household that is adapted to apply at least an electrical load to the fuel processing system.


 2.  The system of claim 1, wherein the fuel processing system is in communication with a household that is adapted to apply thermal loads to the fuel processing system, and further wherein the thermal energy recovery system is adapted to satisfy
at least a portion of the thermal loads.


 3.  The system of claim 1, wherein the recovery system includes a control system with a controller adapted to selectively cause fluid to be drawn from at least one of the plurality of thermal energy reservoirs and delivered into thermal
communication with the fuel processing system.


 4.  The system of claim 1, wherein the recovery system includes a control system with a controller adapted to selectively cause fluid to be drawn from at least one of the plurality of thermal energy reservoirs and delivered into thermal
communication with the household.


 5.  The system of claim 1, wherein the recovery system includes a closed heat exchange loop in thermal communication with the plurality of fuel cells and containing heat exchange fluid.


 6.  The system of claim 5, wherein the closed heat exchange loop is in thermal communication with a thermal energy reservoir containing a heat exchange fluid adapted to be selectively delivered to at least one thermal energy consuming device.


 7.  The system of claim 1, wherein the potable water supply is adapted to supply water to at least one shower in the household.


 8.  The system of claim 1, wherein the potable water supply is adapted to supply water to at least one dishwasher in the household.


 9.  The system of claim 1, wherein the plurality of thermal energy reservoirs includes at least a first reservoir that contains a first heat exchange fluid and a second reservoir that contains a second heat exchange fluid.


 10.  The system of claim 9, wherein the thermal energy recovery system is adapted to maintain the first and the second heat exchange fluids at different temperatures in the first and the second reservoirs.


 11.  The system of claim 9, wherein the first and the second heat exchange fluids are water.


 12.  The system of claim 9, wherein the first and the second heat exchange fluids have the same composition.


 13.  The system of claim 9, wherein the first and the second heat exchange fluids have different compositions.


 14.  The system of claim 9, wherein at least one of the first and the second heat exchange fluids is not water.


 15.  The system of claim 9, wherein at least one of the first and the second heat exchange fluids is not water or air.


 16.  The system of claim 1, wherein the thermal energy recovery system is adapted to produce a heated air stream and to deliver the heated air stream to the household.


 17.  The system of claim 1, wherein the fuel cell stack includes a cathode chamber exhaust, and further wherein the recovery system is further adapted to recover thermal energy from the cathode chamber exhaust.


 18.  The system of claim 1, wherein the fuel processor includes a combustion region adapted to combust a fuel stream to heat the fuel processor and further wherein the recovery system is adapted to recover thermal energy from the combustion
region of the fuel processor.


 19.  The system of claim 1, wherein the fuel processor includes an exhaust from which an exhaust stream is emitted from the fuel processor, and further wherein the recovery system is adapted to recover thermal energy from the exhaust stream.


 20.  The system of claim 1, wherein the recovery system includes a manifold assembly adapted to selectively draw fluid from at least one of the plurality of thermal energy reservoirs and to deliver the fluid into thermal communication with the
household.


 21.  A system for recovering thermal energy from a fuel processing system, comprising: a fuel processing system including a fuel processor and a fuel cell stack, wherein the fuel processor is adapted to receive a feedstock and produce a product
hydrogen stream therefrom, wherein the fuel cell stack includes a plurality of fuel cells adapted to receive the product hydrogen stream and to produce an electric current therefrom, wherein the fuel processing system is in communication with a household
that is adapted to apply at least electrical loads to the fuel processing system;  a thermal energy recovery system adapted to recover thermal energy from the fuel processing system and including a plurality of thermal energy reservoirs that each are
adapted to selectively receive and store a supply of heat exchange fluid and a delivery system adapted to selectively deliver heat exchange fluid from at least one of the plurality of thermal energy reservoirs into thermal communication with the fuel
processing system to recover thermal energy therefrom, wherein at least one of the thermal energy reservoirs forms at least a portion of a potable hot water supply for the household that is adapted to apply at least an electrical load to the fuel
processing system, wherein the recovery system includes a manifold assembly adapted to selectively draw fluid from at least one of the plurality of thermal energy reservoirs and to deliver the fluid into thermal communication with the household, and
further wherein the manifold assembly includes a body and a plurality of inlets adapted to receive selectively heat exchange fluid from the plurality of reservoirs and at least one outlet adapted to deliver the heat exchange fluid into thermal
communication with the household.


 22.  The system of claim 21, wherein the manifold assembly is adapted to receive and mix heat exchange fluid from more than one of the plurality of reservoirs.


 23.  The system of claim 22, wherein the system further includes a control system adapted to control mixing of the heat exchange fluid from the more than one of the plurality of reservoirs.


 24.  The system of claim 1, wherein the fuel processor is adapted to produce the product hydrogen stream via a steam reforming reaction.


 25.  A system for recovering thermal energy from a fuel processing system, comprising: a fuel processing system including a fuel processor and a fuel cell stack, wherein the fuel processor is adapted to receive a feedstock and produce a product
hydrogen stream therefrom, wherein the fuel cell stack includes a plurality of fuel cells adapted to receive the product hydrogen stream and to produce an electric current therefrom, wherein the fuel processing system is in communication with a household
that is adapted to apply at least electrical loads to the fuel processing system;  a thermal energy recovery system adapted to recover thermal energy from the fuel processing system and including a thermal energy reservoir adapted to selectively receive
and store a supply of heat exchange fluid and a delivery system adapted to selectively deliver heat exchange fluid from the thermal energy reservoir into thermal communication with the fuel processing system to recover thermal energy therefrom, wherein
the thermal energy reservoir includes at least one of a swimming pool, a sauna, and a hot tub associated with the household that is adapted to apply at least electrical loads to the fuel processing system.


 26.  The system of claim 25, wherein the fuel processor is adapted to produce the product hydrogen stream via a steam reforming reaction.  Description  

FIELD OF THE INVENTION


The present invention relates generally to fuel processing systems, and more particularly to a system and method for harvesting the thermal energy produced by the fuel processing system.


BACKGROUND AND SUMMARY OF THE INVENTION


Fuel processing systems include a fuel processor and a fuel cell stack.  Fuel processors produce hydrogen gas from a feedstock.  One type of fuel processor is a steam reformer, which reacts steam with an alcohol or hydrocarbon at an elevated
temperature to produce a product stream containing hydrogen gas.  The product stream is delivered to the fuel cell stack, which produces an electric current therefrom.  This electric current can be used to satisfy the electric load of an associated
energy-consuming device, such as a household, vehicle, boat, generator and the like.  A byproduct of producing the electric current is heat, which is formed when protons liberated from the hydrogen gas in the anode chamber of a fuel cell react with
electrons and oxygen in the cathode chamber to form water.


Besides being able to satisfy the electrical demands of the associated device, the fuel processing system also provides a harvestable source of thermal energy.  For example, heat may be harvested from the fuel cell stack directly, or from the
exhaust from the fuel cell stack's cathode chamber.  If the fuel processor utilizes a combustion region to maintain the processor within selected elevated temperature ranges, the exhaust from this combustion region may also be tapped to harvest thermal
energy.


Therefore, a fuel processing system offers several avenues for recovering thermal energy that otherwise would be lost.  The present invention provides a system and method for not only recovering thermal energy from the fuel processing system, but
also maintaining and controlling the utilization of this recovered thermal energy to meet the thermal loads of one or more associated devices.


Many other features of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings in which preferred embodiments incorporating the
principles of this invention are disclosed as illustrative examples only. 

BRIEF DESCRIPTION OF THE DRAWINGS


FIG. 1 is a schematic diagram of a fuel processing system according to the present invention adapted to recover thermal energy from an exhaust stream of a fuel processor.


FIG. 2 is a schematic diagram of another embodiment of the fuel processing system of FIG. 1 adapted to recover thermal energy from a cathode chamber exhaust stream of a fuel cell stack.


FIG. 3 is a schematic diagram of another embodiment of the fuel processing system of FIG. 1 adapted to recover thermal energy from the fuel cell stack directly.


FIG. 4 is an enlarged fragmentary diagram schematically illustrating a portion of the thermal energy recovery system and fuel cell stack of FIG. 3.


FIG. 5 is the diagram of FIG. 4 showing another embodiment of the thermal recovery system and fuel cell stack.


FIG. 6 is a schematic diagram of a fuel processing system according to the present invention that includes the thermal energy recovery system of the embodiments of FIGS. 1-3.


FIG. 7 is a schematic diagram of an embodiment of the thermal energy reservoir of FIGS. 1-3.


FIG. 8 is a schematic diagram showing a variation of the thermal energy reservoir of FIG. 7.


FIG. 9 is a schematic diagram of an embodiment of the thermal energy reservoir of FIG. 6.


FIG. 10 is a schematic diagram of a variation of the thermal energy reservoir of FIG. 9.


FIG. 11 is a schematic diagram of another embodiment of the thermal energy reservoir of FIG. 6.


DETAILED DESCRIPTION AND BEST MODE OF THE INVENTION


A fuel processing system is shown in FIG. 1 and indicated generally at 10.  System 10 includes a fuel processor 12 and a fuel cell stack 14.  Fuel processor 12 produces hydrogen gas from water and a reforming feedstock, typically comprising an
alcohol or a hydrocarbon.  The hydrogen gas is used by the fuel cell stack to produce an electric current, as will be discussed in more detail subsequently.  The current may be used to meet the electric loads applied by an associated electrical device
16, such as a vehicle, boat, generator, household, etc.


It should be understood that device 16 is schematically illustrated in the Figures and is meant to represent one or more devices adapted to receive electric current from the fuel processing system.  Furthermore, the fuel processing system
described herein has been schematically illustrated to include the principle components of the system, namely fuel processor 12, fuel cell stack 14, and the thermal energy recovery system disclosed herein.  It should be understood that the fuel
processing systems described herein may include additional components, such as disclosed in copending U.S.  patent application Ser.  No. 09/190,917, the disclosure of which is hereby incorporated by reference.  Other suitable fuel processors with which
the present invention may be implemented include other steam reformers, or fuel processors that produce hydrogen by partial oxidation of a hydrocarbon or alcohol vapor, or by a combination of partial oxidation and steam reforming a hydrocarbon or an
alcohol vapor, or by pyrollysis of a hydrocarbon or alcohol vapor.


Fuel processor 12 normally operates at an elevated temperature and is maintained within selected temperature ranges by a heating assembly 18.  In many fuel processors, the heating assembly includes a combustion region 20 in which a fuel is
combusted to produce the heat required to maintain the fuel processor within the desired temperature range.  A variety of fuels may be used, including hydrogen gas produced by the fuel processor, propane or other flammable gases, combustible liquid
fuels, etc. When heating assembly 18 includes a combustion region 20, it will also include an exhaust stream 22 from which the hot gases from the combustion region are expelled from the fuel processor.  This exhaust stream may be tapped to harvest, or
recover, the thermal energy of the gases contained within.


In FIG. 1 an embodiment of a thermal energy recovery system is shown and generally indicated at 30.  System 30, which may also be referred to as a heat reservoir system or heat recovery system, is adapted to recover at least a portion of the heat
capacitance of the fuel processing system.  As used herein "heat capacitance" is meant to refer to the thermal energy of the system that would otherwise not be recovered.


System 30 includes a heat reservoir 32 that is configured to store the recovered thermal energy.  Reservoir 32 includes a heat exchange fluid 34 that flows through a heat exchange loop 36 that includes a heat exchanger 38.  In heat exchanger 38,
through which exhaust stream 22 also passes, the heat exchange fluid is heated by the hotter exhaust stream.  Plate-type heat exchangers have proven effective, although it is within the scope of the present invention that any suitable form of heat
exchanger may be used.


Heat exchange fluid 34 may be any suitable fluid capable of being heated by one of the sources of thermal energy described herein.  Examples of suitable heat exchange fluids include air, water, glycols, and water-glycol mixtures, although other
suitable fluids may be used, depending upon the particular operating conditions and requirements of the particular system and the environment in which it is used.  For example, glycol and glycol-water fluid systems may be preferred when the fuel
processing system is used in environments where freezing temperatures are encountered.  When water is used, it may be desirable to use deionized water such as when purified water is required, however, in other systems potable water may be used, and even
consumed, by the associated device.


Fluid 34 may be passed through the heat exchange loop only a single time, or the fluid may be recycled through the loop multiple times, or even continuously.  When a once-through cycle is used, the heated fluid may be transported directly to
device 16, instead of initially returning to reservoir 32, as shown in FIG. 1.  In most applications, it will be desirable to have a continuous recycle of the heat exchange fluid, with a larger volume of heated fluid stored in the reservoir and
maintained within selected temperature ranges by recycling the fluid through loop 36.


When it is desirable to use the heated fluid to meet the thermal load applied by device 16, or any other thermal energy consuming device or devices, the desired flow of fluid 34 may be pumped or otherwise transported to the device, such as
through conduit 40.  In some applications, the transported fluid will be consumed at the device.  In others, it will return to reservoir 32 via conduit 42 after being used to provide heating at device 16.


Examples of situations where the fluid will be consumed at device 16 include embodiments where water is the heat exchange fluid.  This heated water may be used to provide some or all of the hot water needs of the device.  For example, if device
16 includes one or more households, thereby including one or more showers, dish washers, clothes washers, sinks, etc., the required hot water may be provided by system 30.  In some applications, the heated water delivered by system 30 may be provided at
the desired temperature for use by device 16.  In others, it may be delivered at a preheated temperature that is lower than the desired temperature and then heated to the desired temperature at device 16, such as by a water heater.  When air is the heat
exchange fluid, the heated air may be pumped to device 16 to provide heating thereto.  Air will typically be a once-through heat exchange fluid, in that it will typically pass through heat exchanger 38 and then be delivered directly to device 16.  As
discussed, other heat exchange fluids may be used as well, depending on the particular needs of device 16.


Water may also be used for heating at device 16 and then returned to system 30.  Similarly, fluid systems containing glycols or other fluids that are harmful to humans will typically be used for heating and then recycled to system 30.  When a
system containing a glycol or other fluid that is not consumed at device 16, this fluid may be recycled through device 16 to provide heating thereto, or it may be used to heat a fluid, such as air or water, that is consumed at device 16.


Another embodiment of the heat recovery system is schematically illustrated in FIG. 2.  In this embodiment, system 30 is adapted to recover thermal energy from an exhaust stream from the cathode chamber of fuel cell stack 14.  Fuel cell stack 14
includes one or more fuel cells adapted to produce an electric current from the hydrogen gas produced by the fuel processor.  An example of a suitable fuel cell is a proton exchange membrane (PEM) fuel cell, in which hydrogen gas is catalytically
dissociated in the fuel cell's anode chamber 44 into a pair of protons and electrons.  The liberated protons are drawn through an electrolytic membrane 46 into the fuel cell's cathode chamber 48.  The electrons cannot pass through the membrane and
instead must travel through an external circuit to reach the cathode chamber.  The net flow of electrons from the anode to the cathode chambers produces an electric current, which can be used to meet the electrical load being applied by device 16.  In
the cathode chamber, the protons and electrons react with oxygen to form water and heat.  This heat, or thermal energy, is exhausted from the fuel cell stack through an exhaust stream 50.  It is within the scope of the present invention that any other
suitable type of fuel cell may be used.  For example, alkaline fuel cells may be used.


As shown in FIG. 2, system 30 may harvest the thermal energy of exhaust stream 50 via a heat exchange loop 52 and heat exchanger 54.  Similar to the embodiment of system 30 shown in FIG. 1, heat exchange fluid 34 is pumped through loop 52.  The
cooler heat exchange fluid is heated by the hotter exhaust stream 50 in heat exchanger 54.  The heated fluid is returned to reservoir 32, where it may be used to satisfy the thermal demands of device 16, such as through conduit 40.


As shown in FIG. 3, heat recovery system 30 may also be adapted to harvest thermal energy from fuel cell stack 14 directly.  As discussed, fuel cell stack 14 is typically comprised of multiple fuel cells that are coupled together to collectively
produce sufficient current to satisfy the electrical loads of device 16.  The number of such cells is typically selected based on the available size of the stack and the current required by the device.  For example, fuel processing systems implemented on
vehicles will typically need to occupy less space and have less available weight than systems implemented for use in a household.  In FIG. 3, a heat exchange loop 60 is shown transporting heat exchange fluid 34 through fuel cell stack 14.


In FIGS. 4 and 5, two examples of heat exchange loops are shown for recovering thermal energy directly from fuel cell stack 14.  In FIG. 4, heat loop 60 includes a plurality of conduits 62 that flow between the fuel cells 64 comprising fuel cell
stack 14 to recover thermal energy therefrom.  In FIG. 4, conduits 62 are shown passing between each fuel cell 64, however, it should be understood that conduits 62 do not necessarily pass between every adjacent fuel cell 64.  For example, the conduits
may pass between every other fuel cell, every third fuel cell, etc., depending upon such factors as user preferences, thermal management within the fuel cell stack, the size of the conduits, the available thermal energy in stack 14, etc.


FIG. 5 also schematically illustrates the use of an intermediate heat exchange loop.  As shown, heat exchange loop 60 from reservoir 32 does not directly pass through fuel cell stack 14.  Instead, it passes through a heat exchanger 66, through
which another heat exchange loop 68 also passes.  Loop 68, which may also be referred to as an intermediate heat exchange loop, includes conduits 70 that pass between selected fuel cells to recover thermal energy therefrom.  As shown, conduits 70 pass
between every second fuel cell, but as discussed, the specific spacing of the cells and conduits may vary.  Heat exchange fluid is circulated through intermediate heat exchange loop by a pump assembly 71 that includes one or more pumps adapted to pump
the particular heat exchange fluid in loop 68.


An intermediate heat exchange loop may be desirable if there is a concern that metal ions may be introduced into the fuel cell stack through the heat exchange fluid 34.  As a step to prevent this from occurring, it may be desirable to use a
closed, or sealed, intermediate heat loop filled with a heat exchange fluid such as deionized water.  The heat recovered by this closed loop can then be transferred to another heat exchange loop, such as loop 60, which contains the heat exchange fluid
used in reservoir 32.  Another example of when such an intermediate heat exchange loop may be desirable is when the heat exchange fluid contains glycols or other non-potable substances.


It should be understood that the invented thermal energy recovery system 30 may include any or all of the heat exchange loops described above.  An example of such a composite system is shown in FIG. 6 and includes each of the previously discussed
primary heat exchange loops, 36, 52 and 60, and may include any number of intermediate heat exchange loops.  Also shown in FIG. 6 is a hydrogen storage device 72, such as a storage vessel or hydride bed, through which hydrogen gas may be directed through
valve assembly 74 when the quantity of hydrogen gas produced by fuel processor 12 exceeds the hydrogen needs of fuel cell stack 14.


The heat, or thermal energy, reservoir 32 described above is presented in further detail in FIGS. 7-11.  An example of such a reservoir adapted for use with a single heat exchange loop 80 is shown in FIG. 7.  Loop 80 includes output and input
streams 82 and 84, and may represent any of the heat exchange loops described herein, such as loops 36, 52 or 60.  Also shown in FIG. 7 are conduits 40 and 42 that deliver and (optionally) return fluid from device 16.


Reservoir 32 includes at least one fluid storage vessel 86 in which the heat exchange fluid is stored.  A pump assembly 88 includes at least one pump adapted to draw fluid from vessel 86 and transport the fluid through output stream 82.  Examples
of a suitable vessel include open and closed tanks.  The specific construction of the storage vessels and pump assemblies may vary, depending upon the particular heat exchange fluid being used and the intended use of that fluid.  For example, water may
be stored in closed tanks when it is intended for use as the potable hot water supply for a household or other structure, however, it may be stored in open tanks when it is intended for other applications.  Similarly, glycol and glycol-water systems will
tend to be stored in closed tanks, and air will tend to be stored in pressurized tanks.  Other examples of vessels that are within the scope of the present invention are pools, saunas, hot tubs and the like.  For example, a user's swimming pool may be
maintained at a desired heated temperature through the heat recovery system of the present invention without requiring the user to incur the heating bill otherwise required to heat the pool.


In FIG. 8, reservoir 32 is shown including a control system 90.  Control system 90 includes a controller 92 that directs the operation of pump assembly 88 responsive to programmed instructions and/or inputs from sensors and user inputs. 
Controller 92 may be implemented on any suitable digital or analog circuit.  Controller 92 communicates with a sensor assembly 94 that monitors such variables as the temperature and fluid level in vessel 86.  For example, if the temperature of the fluid
within vessel 86 is hotter than a desired temperature, either additional fluid may be added from a supply (not shown), or the rate at which the fluid is recycled may be slowed or stopped to allow the fluid to cool.  On the other hand, if the temperature
of the fluid is lower than desired, the recycle rate may be increased within acceptable limits, some of the stored fluid may be removed to an external storage unit or supply, etc. Similarly, if there is too little fluid in the tank, the controller can
direct additional fluid to be added.  The controller may also stop the operation of pump assembly 88 should there be less than a determined minimum level of fluid within vessel 86.


Controller 92 may also receive inputs from sensors and controllers not shown in the Figures.  For example, the controller may include a sensor (not shown) that measures the rate of operation of the fuel processor, and adjusts the rate at which
fluid is pumped through loop 36 accordingly.  Similarly, a sensor may measure the rate of operation of the fuel cell stack and adjust the rate at which fluid is pumped through loop 60 accordingly.  As used herein, the control system and associated pump
assembly, fluid conduits and/or manifold assembly may be referred to collectively as a delivery system.


In FIG. 9, reservoir 32 is shown adapted for use in the composite heat recovery system shown in FIG. 6.  As shown, reservoir 32 includes inputs and outputs 100/102, 104/106 and 108/110 respectively corresponding to loops 36, 52 and 60, as well as
conduits 40 and 42 in communication with device 16.  Also shown are pump assemblies 112, 114 and 116, which are adapted to pump fluid through loops 36, 52 and 60, respectively.


FIG. 10 is similar to the embodiment of reservoir 32 shown in FIG. 9, except further including the control system 90, including controller 92 and sensor 94 assembly, of FIG. 8.


As discussed, the reservoir may include one or more vessels for storing heat exchange fluid.  An example of such a reservoir is shown in FIG. 11 and indicated generally at 118.  As shown, reservoir 118 includes three vessels 120, 122 and 124,
from which input and output streams 126 and 128 respectively deliver and remove fluid.  It is within the scope of the present invention that more or less vessels than shown in FIG. 11 may be used, and that the vessels may be of the same or different
construction and sizes.  Similarly, the vessels may each house the same or different heat exchange fluids, and the fluids stored within the vessels may be maintained at the same or different temperatures.


A benefit of having multiple vessels is that the volume of fluid being recycled through the heat recovery system may be controlled depending on the operation of fuel processing system 10.  When the system is operating in an idle mode or low-level
operating mode, then it will have less recoverable thermal energy than when operating at its maximum state of operation.  Therefore, the volume of fluid may be varied, depending upon the desired temperature to which the fluid will be heated and the fuel
processing system's ability to supply the required thermal energy.


Reservoir 118 further includes a manifold assembly 130 through which fluid is pumped by a pump assembly from one or more of the vessels and then selectively heat exchanged with any of the sources of thermal energy described herein.  The heated
fluid from any of the vessels or from the heat exchange loops returning to the manifold assembly can be selectively delivered to device 16, such as through conduits 40 and 42.


The selection of the particular vessel to draw fluid from and the rate at which fluid is drawn from the selected vessel or vessels is controlled by a control system 132, which communicates with the manifold assembly and the pumps assembly
associated therewith.  Control system 132 includes a controller 133, which communicates with sensor assemblies 134 within each of the vessels, as discussed above with respect to the controller and sensor assembly of FIG. 8.


As shown, manifold 130 includes inputs and outputs 136 and 138 that correspond to the inputs and outputs of the vessels.  Alternatively, manifold assembly 130 may include one or more inputs or outputs 140 and 142 through which fluid from more
than one vessel may be passed.  The latter scenario is most applicable when the vessels contain the same fluid at the same or similar temperatures, while the formal scenario is applicable regardless of the composition or temperature of the fluids within
the vessels.  It may also be used to mix fluid streams at different temperatures to produce a composite stream at a desired temperature.  Similarly, inputs and outputs 140 and 142 may be used to deliver and (optionally) return mixtures of two or more
different fluids, with the mix ratio controlled by control system 132.


As an example of the fuel processing system's ability to provide recoverable thermal energy, a fuel cell stack with an electrical power output of approximately 3500 kW will produce approximately 12,000 Btu/hr of usable heat.  Therefore, over a
twenty-four hour operating period, the heat recovery system could heat 530 gallons of water from approximately 50.degree.  F. to approximately 115.degree.  F.


The invented thermal energy recovery system and method effectively increase the efficiency of the fuel processing system by recovering and utilizing thermal energy that otherwise would be lost.  By using this recovered thermal energy to meet the
thermal requirements of the associated device, the energy requirements of the device are reduced.  The system also enables the fuel processing system to meet thermal loads that otherwise would be beyond the capacity of the fuel processing system.  For
example, when the applied thermal and/or electric load exceeds the capacity of the fuel processing system, the thermal energy stored in the reservoir system may be used to satisfy these demands.  Similarly, when the fuel processing system is producing
more thermal energy than needed by device 16, this excess energy may be stored by the reservoir system to be used when the thermal load increases.  Effectively, the reservoir system enables the thermal demands placed upon the fuel processing system to be
buffered, or leveled out, as they fluctuate with the demands of device 16.


While the invention has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible.  It is intended that any singular
terms used herein do not preclude the use of more than one of that element, and that embodiments utilizing more than one of any particular element are within the spirit and scope of the present invention.  For example, the above-described heat exchange
loops may include more than one fluid conduit.  Similarly, the heat exchangers described herein may include more than one actual heat exchange unit.  Applicants regard the subject matter of the invention to include all novel and non-obvious combinations
and subcombinations of the various elements, features, functions and/or properties disclosed herein.  No single feature, function, element or property of the disclosed embodiments is essential to all embodiments.  The following claims define certain
combinations and subcombinations that are regarded as novel and non-obvious.  Other combinations and subcombinations of features, functions, elements and/or properties may be claimed through amendment of the present claims or presentation of new claims
in this or a related application.  Such claims, whether they are broader, narrower or equal in scope to the original claims, are also regarded as included within the subject matter of applicants' invention.


* * * * *























				
DOCUMENT INFO
Description: The present invention relates generally to fuel processing systems, and more particularly to a system and method for harvesting the thermal energy produced by the fuel processing system.BACKGROUND AND SUMMARY OF THE INVENTIONFuel processing systems include a fuel processor and a fuel cell stack. Fuel processors produce hydrogen gas from a feedstock. One type of fuel processor is a steam reformer, which reacts steam with an alcohol or hydrocarbon at an elevatedtemperature to produce a product stream containing hydrogen gas. The product stream is delivered to the fuel cell stack, which produces an electric current therefrom. This electric current can be used to satisfy the electric load of an associatedenergy-consuming device, such as a household, vehicle, boat, generator and the like. A byproduct of producing the electric current is heat, which is formed when protons liberated from the hydrogen gas in the anode chamber of a fuel cell react withelectrons and oxygen in the cathode chamber to form water.Besides being able to satisfy the electrical demands of the associated device, the fuel processing system also provides a harvestable source of thermal energy. For example, heat may be harvested from the fuel cell stack directly, or from theexhaust from the fuel cell stack's cathode chamber. If the fuel processor utilizes a combustion region to maintain the processor within selected elevated temperature ranges, the exhaust from this combustion region may also be tapped to harvest thermalenergy.Therefore, a fuel processing system offers several avenues for recovering thermal energy that otherwise would be lost. The present invention provides a system and method for not only recovering thermal energy from the fuel processing system, butalso maintaining and controlling the utilization of this recovered thermal energy to meet the thermal loads of one or more associated devices.Many other features of the present invention will become manifest to those versed in the ar